Identification of novel cis-acting elements, IDE1 and IDE2, of the barley IDS2 gene promoter conferring iron-deficiency-inducible, root-specific expression in heterogeneous tobacco plants
Article first published online: 6 NOV 2003
The Plant Journal
Volume 36, Issue 6, pages 780–793, December 2003
How to Cite
Kobayashi, T., Nakayama, Y., Itai, R. N., Nakanishi, H., Yoshihara, T., Mori, S. and Nishizawa, N. K. (2003), Identification of novel cis-acting elements, IDE1 and IDE2, of the barley IDS2 gene promoter conferring iron-deficiency-inducible, root-specific expression in heterogeneous tobacco plants. The Plant Journal, 36: 780–793. doi: 10.1046/j.1365-313X.2003.01920.x
- Issue published online: 6 NOV 2003
- Article first published online: 6 NOV 2003
- Received 15 June 2003; revised 29 August 2003; accepted 10 September 2003.
- cis-acting elements;
- Fe-deficiency-inducible expression;
- promoter analysis;
- root-specific expression
The molecular mechanisms of plant responses to iron (Fe) deficiency remain largely unknown. To identify the cis-acting elements responsible for Fe-deficiency-inducible expression in higher plants, the barley IDS2 (iron deficiency specific clone no. 2) gene promoter was analyzed using a transgenic tobacco system. Deletion analysis revealed that the sequence between −272 and −91 from the translational start site (−272/−91) was both sufficient and necessary for specific expression in tobacco roots. Further deletion and linker-scanning analysis of this region clearly identified two cis-acting elements: iron-deficiency-responsive element 1 (IDE1) at −153/−136 (ATCAAGCATGCTTCTTGC) and IDE2 at −262/−236 (TTGAACGGCAAGTTTCACGCTGTCACT). The co-existence of IDE1 and IDE2 was essential for specific expression when the −46/+8 region (relative to the transcriptional start site) of the CaMV 35S promoter was used as a minimal promoter. Expression occurred mainly in the root pericycle, endodermis, and cortex. When the −90/+8 region of the CaMV 35S promoter was fused, the −272/−227 region, which consists of IDE2 and an additional 19 bp, could drive Fe-deficiency-inducible expression without IDE1 throughout almost the entire root. The principal modules of IDE1 and IDE2 were homologous. Sequences homologous to IDE1 were also found in many other Fe-deficiency-inducible promoters, including: nicotianamine aminotransferase (HvNAAT)-A, HvNAAT-B, nicotianamine synthase (HvNAS1), HvIDS3, OsNAS1, OsNAS2, OsIRT1, AtIRT1, and AtFRO2, suggesting the conservation of cis-acting elements in various genes and species. The identification of novel cis-acting elements, IDE1 and IDE2, will provide powerful tools to clarify the molecular mechanisms regulating Fe homeostasis in higher plants.